Understand the terms flood likelihood and impact to get the most out our Flood Awareness Map.
Before searching for a property on Council’s Flood Awareness Map, it is important to understand the terms flood likelihood and impact.
The terms 'likelihood' and 'impact' are used by Council to explain the chances of floods occurring. These terms are used in the Flood Awareness Map, which is an awareness tool to display the probability of a flood occurring from one or more sources including creek, river and storm tide. It also shows the impact of overland flow flooding.
The Flood Awareness Map does not provide information about the depth or speed of flood water.
The Flood Awareness Map uses the term likelihood to describe the chance of river, creek and storm tide flooding happening annually.
This type of flood is considered regular. There is a 1 in 20 chance (5% likelihood) of this type of flooding happening in any year.
Action
Residents and businesses are strongly advised to prepare for flooding to minimise the impact on their home and business.
This type of flood is considered to be irregular. There is a 1 in 100 chance (1% likelihood) of flooding occurring in any year.
Action
Residents and businesses are advised to prepare for flooding to minimise the impact on their home and business.
This type of flood is considered rare. There is a 1 in 500 chance (0.2% likelihood) of flooding occurring in any year.
Action
Residents and businesses should consider how flooding may affect their local area to minimise the impact on their home and business.
This type of flood is considered a very rare or an extreme event. There is a 1 in 2000 chance (0.05% likelihood) of flooding occurring in any year.
Action
Residents and businesses should consider how flooding may affect their local area to minimise the impact on their home and business.
Flood impact is the way we describe the magnitude or severity of overland flow flood events.
Overland flow is run-off that travels over the land during heavy rainfall events. It can be unpredictable, occurring very quickly and for short durations.
This type of overland flow flood is considered regular. There is a 1 in 20 chance (5% likelihood) of flooding occurring in any year.
This overland flow is generally unsafe for people, vehicles and buildings.
Action
Residents and businesses are strongly advised to prepare for flooding to minimise the impact on their home and family.
This type of overland flood is considered to be irregular. There is a 1 in 50 chance (2% likelihood) of flooding occurring in any year.
This overland flow is generally unsafe for people, vehicles and buildings, however these hazards are experienced less frequently than in high impact areas.
Action
Residents and businesses are strongly advised to prepare for flooding to minimise the impact on their home and business.
This type of overland flood is considered irregular. There is a 1 in 100 chance (1% likelihood) of flooding occurring in any year.
This overland flow is generally unsafe for people, vehicles and buildings, however these hazards are experienced less frequently than in high impact areas.
Action
This overland flow is generally safe for people, vehicles and buildings, however, certain areas can experience greater hazards.
You can also view this video on Council's YouTube channel.
This is a video transcript of the Understanding flood likelihood and impact video hosted on Brisbane City Council's YouTube channel. This video is 3 minutes and 13 seconds long.
>>Female voice: Brisbane City Council’s Flood Awareness Map is an interactive online tool to help residents understand the risk of flooding on a property.
Council uses the terms likelihood and impact to explain the chances of flooding from one or more sources.
Residents and businesses must consider how flooding may affect their property and neighbourhood.
Steps should be taken to plan and prepare to minimise flooding impacts on your home, business and family.
The Flood Awareness Map uses the term likelihood to describe the possibility of flooding from rivers, creeks and storm tides happening annually.
Flood likelihood is broken down into four categories: high, medium, low and very low. Each category of flood likelihood is shown as a different shade of colour on the Flood Awareness Map.
High likelihood describes a type of flood that is almost certain to occur during a single lifetime, possibly more than once.
There is a 1 in 20 chance or a 5% possibility for a flood of this size to occur in any year. Residents and businesses are strongly advised to prepare for flooding, to minimise the impact on their homes, business and family. Search ‘Be Prepared’ on Council’s website for tips and advice.
Medium likelihood describes the type of flood likely to occur during a single lifetime. There is a 1 in 100 chance or a 1% possibility for a flood of this size to happen in any year.
Council also maps rare and very rare flood events, which are shown as low and very low likelihoods. Although these are not as likely as high or medium likelihood flood events, they may still occur.
All modelled flood events should be taken seriously, and steps taken to prepare. Find out more information about how to prepare for flooding on Council’s website.
The Flood Awareness Map uses the term impact to describe the severity of potential overland flow flood events. Overland flow can be fast-moving and unpredictable, with varying depths and extents.
Overland flow impact is broken down into three categories: high, medium and low.
High impact overland flow is almost certain to occur during a single lifetime of 70 years.
There is a 1 in 20 chance or a 5% possibility for high impact overland flow occurring in any year.
Due to the depth and unpredictability of overland flow water, it is generally unsafe for people, vehicles and buildings.
Medium impact overland flow is very likely to occur during a single lifetime. There is a 1 in 50 chance or a 2% possibility for medium-impact overland flow occurring in any year.
Low impact overland flow is likely to occur during a single lifetime. There is a 1 in 100 chance or a 1% possibility for low impact overland flow occurring in any year.
Residents and businesses are strongly advised to prepare for all types of overland flow to minimise the impact on their home, business and family.
Use Council’s Flood Awareness Map to check your property’s flood likelihood and overland flow impact to understand how your home or business may be affected.
Being flood resilient means you can plan, prepare, respond and return to normal life with minimal disruption following flooding.
Visit Council’s website to find more information on flood resilience and how to be prepared for flooding.